Direct-Reading Inhalable Dust Monitoring - An Assessment of Current Measurement Methods

Direct-reading dust monitors designed specifically to measure the inhalable
fraction of airborne dust are not widely available. Current practice therefore
often involves comparing the response of photometer-type dust monitors with the
concentration measured with a reference gravimetric inhalable sampler, which is
used to adjust the dust monitor measurement. However, changes in airborne
particle size can result in significant errors in the estimation of inhalable
concentration by this method.

The main aim of this study was to assess how these dust monitors behave when
challenged with airborne dust containing particles in the inhalable size range
and also to investigate alternative dust monitors whose response might not be
as prone to variations in particle size or that could be adapted to measure
inhalable dust concentration. Several photometer-type dust monitors and a
Respicon TM, tapered element oscillating microbalance (TEOM) personal dust
monitor (PDM) 3600, TEOM 1400, and Dustrak DRX were assessed for the
measurement of airborne inhalable dust during laboratory and field trials. The
PDM was modified to allow it to sample and measure larger particles in the
inhalable size range.

Laboratory results showed that the Respicon, modified PDM, and TEOM 1400
observed good linearity for all types of dust when compared with measurements
made with a reference IOM sampler; the photometer-type dust monitors on the
other hand showed little correlation. The Respicon also accurately measured the
inhalable concentration, whereas the modified PDM underestimated it by ~27%.
Photometer responses varied considerably with changing particle size, which
resulted in appreciable errors in airborne inhalable dust concentration

Similar trends were also observed during field trials. Despite having
limitations, both the modified PDM and Respicon showed promise as real-time
inhalable dust monitors.

Further Information - Source: The Annals of Occupational Hygiene